The present invention relates to systems for providing information to the pilot of an aircraft and, in particular, it concerns a system for providing selected information to a pilot based on his gaze-direction without use of a visual display. In one application, the invention specifically addresses the control interface between a pilot and a weapon system through which the pilot designates and verifies tracking of a target by the weapon system.
The extremely high speed of modern air-to-air combat stretches the capabilities of a human pilot to their limits. Faced with complex aircraft instrumentation and high-tech weapon systems, a pilot is required to achieve split-second reaction times as supersonic aircraft pass each other at relative speeds up to thousands of miles per hour. Various high performance target-seeking air-to-air missiles have been developed to operate under these conditions. Nevertheless, the process of cueing such missiles and verifying that they are locked-on to the correct target before firing may be extremely difficult for the pilot, especially while simultaneously flying an aircraft under conditions of constantly varying orientation, extreme inertial forces and high stress.
To facilitate rapid designation of targets, a head-up display is typically used to indicate the current cueing direction. A display symbol representing the direction of regard of the missile seeker is brought into superposition with a directly viewed target and the seeker is then allowed to track the target. If the pilot sees that the display symbol is following the viewed target, he knows that the tracking is proceeding properly and can proceed to fire the missile.
Many state-of-the-art systems employ a helmet-mounted head-up display. In this case, the seeker typically follows an optical axis of the display which moves together with the helmet, the helmet position being monitored either by a magnetic or an optical system. Cueing is achieved by the pilot turning his head, and hence the helmet, to bring the optical axis into alignment with the target. Examples of such systems are commercially available, amongst others, from Elbit Ltd. (Israel) and Comulus (South Africa).
Despite the major technological advances which have been made in the implementation of helmet-mounted displays and cueing systems, such systems still suffer from a large number of disadvantages, as will now be detailed.
Firstly, the components mounted in the helmet add greatly to the weight of the helmet. This weight becomes multiplied numerous times under high-acceleration conditions, becoming a major source of fatigue and stress for the pilot.
Secondly, these systems generally require alignment of the optical axis of the helmet with the target to be designated. This limits operation of the system to the angular range of helmet motion which the pilot can achieve. This is typically smaller than the actual field of view both of the pilot and of the seeker of the air-to-air missiles, thereby limiting performance unnecessarily. Furthermore, shifting of the entire head together with the heavy helmet to the required angle under high acceleration conditions may require great effort, and may cause significant delay in the cueing procedure.
Thirdly, the helmet-mounted display typically requires very substantial connections between the helmet and other devices within the aircraft. These connections generally include a significant power supply and electrical and/or optical fibers for carrying projected information for the display. Such connections pose a significant safety hazard for the pilot, particularly with respect to emergency ejection where a special guillotine is required to sever the connections in case of emergency. The supply of a high voltage power line to within the helmet is also viewed as a particular safety hazard.
Finally, the integration of a head mounted display and cueing system into the aircraft systems is a highly expensive project, requiring adaptation of numerous subsystems, with all the complications of safety and reliability evaluation procedures and the like which this entails.
In addition to the specific issue of cueing and verifying correct tracking of weapon systems, modern aircraft include multiple information systems which in many cases generate information relating to objects or locations visible to the pilot. Such systems typically include radar and navigation systems of various types, as well as data systems. In many cases, DataLink (DL) systems are provided which can offer a wide variety of information, such as identifying other aircraft as friendly or hostile, identifying the type of aircraft and even provide information regarding the armament of the aircraft. Navigation related information typically includes the identity of various visible landmarks such as mountains or cities. Commercially available examples of such systems in the U.S. include the systems known by the names “Link4” and Link16”. In many cases it would be highly advantageous to provide this information on a head-up display so that it would be visually linked in an intuitive way to the pilot's field of view. This however can only be achieved over a useful field of view by employing a helmet-mounted display with all of the aforementioned disadvantages.
Turning now to the field of eye-motion tracking, various techniques have been developed for identifying the gaze direction of the human eye. Examples of a number of commercially available systems for tracking eye movements may be obtained from ASL Applied Science Laboratories (Bedford, Mass., USA).
U.S. Pat. No. 5,583,795 to Smyth proposes a helmet-mounted apparatus for measuring eye gaze while providing a helmet-mounted display. Brief reference is made to the possibility of using the apparatus for “designating targets” and “weapon system pointing”. Such a system, however, would still suffer from most of the aforementioned shortcomings associated with helmet-mounted display systems.
There is therefore a need for a gaze-actuated information system which would facilitate rapid and reliable cueing and tracking verification of air-to-air missiles without the pilot having to turn his entire head and without requiring substantial additional connections or expensive modification of aircraft systems. It would also be highly advantageous to provide a method for providing information, including confirming that a weapon system is locked-on to a visible target, without requiring use of a visual display.